Law 6. TOSS6.1 Before play commences, a toss shall be conducted and the side winning the toss shall exercise the choice in either Law 6.1.1 or 6.1.2:

6.1.1 to serve or receive first;
6.1.2 to start play at one end of the court or the other.

6.2 The side losing the toss shall then exercise the remaining choice.

Law 7. SCORING SYSTEM
7.1 A match consists of the best of 3 games of 21 points, unless otherwise arranged.
7.2 Every time there is a serve – there is a point scored.
7.3 The side winning a rally adds a point to its score.
7.4 At 20 all, the side which gains a 2 point lead first, wins that game.
7.5 At 29 all, the side scoring the 30th point, wins that game.
7.6 The side winning a game serves first in the next game.

For example, in a doubles match between A & B against C & D. A & B won the toss and decided to serve. A to serve to C. A shall be the initial server while C shall be the initial receiver.

Note that this means:

The order of server depends on the score odd or even same as in singles.

The service courts are changed by the servicing side only when a point is scored. In all other cases, the players continue to stay in their respective service court from where they played previous rally. This shall guarantee alternate server.

Law 8. INTERVAL AND CHANGE OF ENDS
8.1 Players shall change ends

8.1.1 When the leading score reaches 11 points, players have a 60 second interval.8.1.2 A 2 minute interval between each game is allowed.8.1.3 In the third game, players change ends when the leading score reaches 11 points.

8.2 If the ends are not changed as indicated in Law 8.1, it shall be done so as soon as the mistake is discovered and when the shuttle is not in play. The existing score shall stand.

Law 9. SERVICE
9.1 In a correct service:

9.1.1 Neither side shall cause undue delay to the delivery of the service once the server and the receiver are ready for the service. On completion of the backward movement of server’s racket head, any delay in the start of the service (Law 9.2), shall be considered to be an undue delay;9.1.2 The server and the receiver shall stand within diagonally opposite service courts without touching the boundary lines of these service courts;9.1.3 Some part of both feet of the server and the receiver shall remain in contact with the surface of the court in a stationary position from the start of the service (Law 9.2) until the service is delivered (Law 9.3);9.1.4 The server’s racket shall initially hit the base of the shuttle;9.1.5 The whole shuttle shall be below the server’s waist at the instant of being hit by the server’s racket. The waist shall be considered to be an imaginary line round the body, level with the lowest part of the server’s bottom rib;9.1.6 The shaft of the server’s racket at the instant of hitting the shuttle shall be pointing in a downward direction;9.1.7 The movement of the server’s racket shall continue forwards from the start of the service (Law 9.2) until the service is delivered (Law 9.3);9.1.8 The flight of the shuttle shall be upwards from the server’s racket to pass over the net so that, if not intercepted, it shall land in the receiver’s service court (i. e. on or within the boundary lines); and 9.1.9 In attempting to serve, the server shall not miss the shuttle.

9.2 Once the players are ready for the service, the first forward movement of the server’s racket head shall be the start of the service.
9.3 Once started (Law 9.2), the service is delivered when the shuttle is hit by the server’s racket or, in attempting to serve, the server misses the shuttle.
9.4 The server shall not serve before the receiver is ready. However, the receiver shall be considered to have been ready if a return of the service is attempted.
9.5 In doubles, during the delivery of service (Law 9.2, 9.3), the partners may take up any positions within their respective courts, which do not unsight the opposing server or receiver.

Law 12. SERVICE COURT ERRORS
12.1 A service court error has been made when a player:

12.1.1 has served or received out of turn; or
12.1.2 has served or received from the wrong service court;

12.2 If a service court error is discovered, the error shall be corrected and the existing score shall stand.

Law 13. FAULTS
It shall be a ‘fault’:
13.1 if a service is not correct (Law 9.1);
13.2 if, in service, the shuttle:

13.2.1 is caught on the net and remains suspended on its top;
13.2.2 after passing over the net, is caught in the net; or
13.2.3 is hit by the receiver’s partner;

13.3 if in play, the shuttle:

13.3.1 lands outside the boundaries of the court (i. e. not on or within the boundary lines);
13.3.2 passes through or under the net;
13.3.3 fails to pass over the net;
13.3.4 touches the ceiling or side walls;
13.3.5 touches the person or dress of a player;
13.3.6 touches any other object or person outside the court;
(Where necessary on account of the structure of the building, the local badminton authority may, subject to the right of veto of its Member Association, make bye-laws dealing with cases in which a shuttle touches an obstruction).
13.3.7 is caught and held on the racket and then slung during the execution of a stroke;
13.3.8 is hit twice in succession by the same player. However, a shuttle hitting the head and the stringed area of the racket in one stroke shall not be a ‘fault’;
13.3.9 is hit by a player and the player’s partner successively; or
13.3.10 touches a player’s racket and does not travel towards the opponent’s court;

13.4 if, in play, a player:

13.4.1 touches the net or its supports with racket, person or dress;
13.4.2 invades an opponent’s court over the net with racket or person except that the striker may follow the shuttle over the net with the racket in the course of a stroke after the initial point of contact with the shuttle is on the striker’s side of the net;
13.4.3 invades an opponent’s court under the net with racket or person such that an opponent is obstructed or distracted; or
13.4.4 obstructs an opponent, i.e. prevents an opponent from making a legal stroke where the shuttle is followed over the net;
13.4.5 deliberately distracts an opponent by any action such as shouting or making gestures;

13.5 if a player is guilty of flagrant, repeated or persistent offences under Law 16.

Law 14. LETS14.1 ‘Let’ shall be called by the umpire, or by a player (if there is no umpire), to halt play.14.2 It shall be a ‘let”, if:

14.2.1 the server serves before the receiver is ready (Law 9.4);
14.2.2 during service, the receiver and the server are both faulted;
14.2.3 after the service is returned, the shuttle is:

14.2.3.1 caught on the net and remains suspended on its top, or
14.2.3.2 after passing over the net is caught in the net;

14.2.4 during play, the shuttle disintegrates and the base completely separates from the rest of the shuttle;
14.2.5 in the opinion of the umpire, play is disrupted or a player of the opposing side is distracted by a coach;
14.2.6 a line judge is unsighted and the umpire is unable to make a decision; or
14.2.7 any unforeseen or accidental situation has occurred.

14.3 When a ‘let’ occurs, play since the last service shall not count and the player who served last shall serve again.